First off if you want to use Freeview|HD then you will need a video card that does H.264 hardware acceleration and TV software that supports this. What software had you planned to use?

Secondly none of those VGA resolutions are widescreen they are all 4:3 - you won't get ideal results using that TV for a HTPC. HDMI may be a better option but being an older TV you may not get 1:1 pixel mapping via HDMI (that'a ssusming the TV does have HDMI).

TV does have an HDMI input and I have had excellent results using a 1:1 ratio via HDMI and my PS3 and Linux.

I do not want to use a DBT/S card (at this stage). I have a specific program I will be using which will only output via the standard monitor output and can only be used with a UHF signal.

The instruction manual states that regardless of what resolution the TV is fed it will change it to S-XGA. So I guess if I send an S-XGA signal to the TV anyway this will prevent any more procesing than is necessary.

if you're only wanting to use it for the UHF signal then i wouldnt get too stressed about the picture quality... especially as the 'program' you're referring to doesnt exactly enhance the original picture...